So the referee can ask for their opinion, or he can be told theirs, mostly just for penalties and red cards. So, in theory, the ref could send someone off and then have it rescinded by the VAR team. Or award a penalty and then see it reversed. Or the other way round for both - though that is less likely for a penalty unless the game has already stopped.

I guess they won't be together enough to put any of this on the screens at the match (but will on the screens on the TV).

As I have read it The VAR will draw the match refs attention ,via his headpiece, to any incidents and also any reason to allow or disallow a goal or penalty and the match ref will then look at it on the TV screen at the side of the pitch and make the ultimate decision. I could however have misinterpreted that,.